Align the text between editing and display mode, and remove the dead
code. The prompt sign does not have to be part of the text and the
JS parser does not have to retain the code it parses.

Change-Id: I6e41f4fbc2cc863c84677640826d8663bcc648fb
Task-number: QTCREATORBUG-14931
Reviewed-by: hjk <hjk@theqtcompany.com>